President Donald Trump has ordered the resumption of US nuclear weapons testing for the first time in more than three decades, citing the need to match the growing nuclear capabilities of Russia and China.

In a late-night social media post on Wednesday, Trump said he had directed the Department of War to begin testing “on an equal basis” with other nuclear powers. The announcement came just hours before his scheduled meeting with Chinese President Xi Jinping in South Korea — their first in-person engagement since 2019.

“Because of other countries’ testing programs, I have instructed the Department of War to start testing our nuclear weapons on an equal basis,” Trump wrote.

He described the weapons’ “tremendous destructive power” but argued that the United States had “no choice” but to modernise and expand its arsenal to maintain strategic balance. “The process will begin immediately,” he added, without providing details on the timing or locations of the tests.

The decision marks a dramatic reversal of US policy. The United States has not conducted a nuclear test since 1992, when President George H.W. Bush declared a moratorium following the end of the Cold War. The last test, codenamed Divider, took place underground in Nevada and was the nation’s 1,054th nuclear detonation.

Speaking aboard Air Force One after his meeting with Xi, Trump said potential test sites would be announced later, insisting it was “appropriate” for the US to resume testing “given global developments.”

The order comes amid mounting geopolitical tensions. Days earlier, Trump condemned Russia’s test of a nuclear-powered missile reportedly capable of unlimited range. Moscow later confirmed the successful testing of two new nuclear-capable weapons, including the Poseidon underwater drone, though neither involved live nuclear detonations.

Meanwhile, US intelligence agencies have warned that China is rapidly expanding its nuclear stockpile. The Center for Strategic and International Studies (CSIS) estimates that Beijing has doubled its arsenal in five years and could exceed 1,000 warheads by 2030.

According to the Arms Control Association, the US currently holds about 5,225 nuclear warheads, compared to Russia’s 5,580.

Trump’s directive also coincides with the impending expiration of the New Strategic Arms Reduction Treaty (New START) in February 2026 — the last remaining arms control agreement between the US and Russia, which limits each side to 1,550 deployed strategic warheads.

The move has sparked sharp debate among defence experts. Supporters argue that renewed testing will reinforce deterrence and project strength, while critics warn it could trigger a new nuclear arms race and undermine decades of non-proliferation efforts.

The Nevada Test Site, about 65 miles north of Las Vegas, remains functional and could be reactivated for the programme. It was the main hub for nuclear testing during the Cold War.

The US first tested a nuclear device in July 1945 in Alamogordo, New Mexico, before using atomic bombs on Hiroshima and Nagasaki, marking the dawn of the nuclear age.

If implemented, Trump’s order would end a 33-year moratorium on nuclear testing and signal a major shift in global arms control policy — reigniting debates on deterrence, diplomacy, and the future of international security.